An X-ray machine can be used to make photographic images which indicate the internal composition of objects. One well known use is the detection:of broken or fracture bones. A typical X-ray machine is inadequate for some tasks because it is unable to make photographic images of metals. Since a typical X-ray machine is large and requires a power source, it cannot be taken to remote locations without significant expense.
Radiographic cameras are used to make images similar to X-ray images, but with greater flexibility. A radiographic camera can record images of metals which cannot be imaged with an X-ray machine. In addition these cameras are portable and operate without an external power source, and so can take images of objects in their natural environment. Radiographic cameras are used extensively in the oil industry, for example, to check for flaws in metal pipelines which could otherwise cause oil spills.
A typical radiographic camera and source are shown and described in U.S. Pat. Nos. 5,065,033 and 4,827,493, respectively. Each of these patents is assigned to the same assignee as the present invention, and each is hereby incorporated by reference. As shown in FIG. 1 of U.S. Pat. No. 5,065,033, an S-shaped tubing extends from a back end of the camera to a front end. The tubing is surrounded by a radiation shield and encloses a radiographic source at the end of a source cable. A typical radiographic source includes stacked iridium-192 wafers which are welded inside a capsule. Since the radiographic source emits radiation in a line, when the source is in a stored position (as in FIG. 1), only minimal radiation is reflected toward the front end, by which time any power that remains is significantly decreased.
A lock assembly is provided over an opening at the back end of the camera, and a threaded nut blocks an opening at the front end. Control cables are attached to the back end, and a guide cable is screwed to the front end. The lock assembly in the back prevents the radiation source from being pushed out of the front end without first using a key to unlock the camera, and then connecting a control cable. At the front end of a typical camera, a technician removes the threaded nut, and attaches a guide cable with a threaded end over the threaded mount on the housing. When the control cables and guide cable are positioned, the technician operates a hand crank to move a wire in the control cable which pushes the source out of the camera housing and to the end of the guide cable. The end of the guide cable is then positioned on one side of an object which is to be imaged, and photographic cassettes is placed on the other side. Exposure time is set by the technician. When finished, the technician reverses the direction of the crank to retract the source.